REDUCTION OF ARCOIRIS ARTIFACTS IN DIGITAL LIGHT PROJECTION SYSTEMS
I nvention Cam e The present invention relates generally to projection systems and more particularly, to reducing visual artifacts within such systems.
BACKGROUND OF THE INVENTION Digital light processing technology ™ refers to the use of an optical integrated circuit that manipulates the light source. The optical semiconductor, referred to as a digital micro-mirror (DMD) device can be incorporated into a larger projection system. The products that incorporate DMD technology are manufactured for a variety of different applications, including home and commercial theater use. A DMD can include a rectangular array of approximately 1.3 million microscopic mirrors called micro-mirrors. Each micro-mirror is extremely small, measuring less than about one-fifth the width of a human hair. Each micro-mirror is also mounted in articulations to allow the micro-mirror to lean towards the light source or away from the light source under the control of an activating circuit. When leaning towards the light source, it is said that the mirror is in the "on" position, since light is reflected from the light source. When leaning away from the light source, it is said that the mirror is in the "off" position, since light is not reflected
from the power source A control signal provided to the DMD from the converter circuit directs each micro-mirror to turn on or off several times a second. When a mi-mirror is turned on more times than turned off, the micro -mirror reflects a pixel of gray light Conversely, a micro-mirror that shuts off more times than turned on reflects a pixel of darker gray Thus, when a source of light emits white light it is combined with a DM D and a lens, a gray scale projection system is formed. Color projection systems can be constructed by inserting a chromatic wheel in the light path between the DMD and the light source, or in the light path between the DM D and the projection lens At the edges of the color wheel there are light filters to generate red, green and blue light. The white light that emanates from the light source can pass through these filters as the color wheel rotates. colored light Finally, it enters the projection lens for display on the screen. The rotation of the color wheel is coordinated with the control signals provided to the DMD. In this way, each micro-mirror can be turned on and off at a particular speed or by selected time periods, which may vary in accordance with the light filter of the color wheel used to filter the light source for a predetermined period of time. In other words, the on and off states of each mirror-image are coordinated with the rotation of the three color light filters of the color wheel
In the illustration, a micro-mirror for the purpose of generating a purple pixel can be turned on only to cause reflection of the red and blue lz. That is, the mirror-mi-cro can be turned on more times than turned off when the red and blue filters are used to filter the light. The red and blue reflected light is perceived as a particular shade of purple when it is shown in rapid succession in the same projection space. In this way, each micro-mirror can project what is perceived to be a pixel of color of an image. As mentioned, the mutation of the micro-mirrors and the proportion of time in which each micro-mirror is on or paid, is coordinated according to the color light filter used to fi lter the source of l uz. The human visual system integrates the sequential color images and looks for a multi-color image. The color wheel passes only a single color of light through the corresponding filter aligned with the light incident on the wheel. This leads to a situation where the images in red, green and blue do not coincide in time with the projection surface. Small time delays between consecutive color images can cause noticeable visual artifacts in the resulting image. When the observer's eye moves very quickly, the observer can perceive the individual images of red, green and blue. Such is the case i ncl use when the object is put white. This can be perceived as an artifact of arc i ris, which means that images of a different color are not perceived as a single, mixed image. It will be beneficial to provide a projection system with the use of
DMD technology that reduces perceptible visual artifacts, and in particular, rainbow artifacts.
Brief Description of the Invention One aspect of the present invention may include a projection system. The projection system may include a means for sequentially producing color light from a light source. Each color light can be produced for a predetermined color phase, or a period of time. One or more digital micro-mirror devices may be included within the optical path of the color light reproducing medium and the light source. Each digital micro-mirror device may include a plurality of micro-mirrors. At least one of the plurality of micro-mirrors can be activated in response to a control signal that starts during a respective respective portion within each two consecutive color phases to cause reflection of the color light from the medium to produce in sequentially light with color. The projection system may include a lens configured to project light with reflected color from one or more micro-mirror devices onto a projection surface. One or more of the plurality of micro-mirrors can generate at least one pixel with less complex color. A pixel with less complex color is a pixel that has a color generated with the use of more than one color filter from the color wheel. Similarly, a complex image can be an image that includes a complex color. In one embodiment, the control signal may activate one or more of the
plurality of micro-mirrors approximately in the middle or in the end portion within a first of the two color phases In another embodiment, the control signal may activate one or more of the plurality of micro-mirrors approximately at the beginning or in the middle portion within a second of the two color phases Notably, the color signal may cause one or more of the plurality of micro-mirrors to be lit from the middle portion within the first of the two color phases in at least a portion of the second of the two color phases. The means for sequentially producing the light with color may include a color wheel having blue, green and red light filters. Accordingly, one or more of the plurality of micro-mirrors can generate one or more complex images from the sequentially ordered blue, green and red images. The color wheel can also include a clear filter to produce white light. The images White generated with the use of the clear filter may be generated after the blue images and before the red images A white phase generated with the use of the clear filter may be shorter in time than any other color phase. Another aspect of the invention of the present invention may include a projection system having a means to produce blue, green and red light from a light source. Each color may be produced in a sequential order by a predetermined color phase. The projection system may also include At least one digital micro-mirror device to provoke the reflection of different colors of light and a
lens configured to project the different colors of l uz onto a projection surface. Remarkably, a color phase for white light may be shorter than color phases for other colors. In addition, the color phase for white light may be arranged between the color phases for blue light and red light . Another aspect of the present invention may include a method for generating a complex color within the projection system. The method may include (a) generating different light colors sequentially, each or not for a predetermined color phase; and (b) activating at least one micro-mirror that emparts in different respective portions of each of the two consecutive color phases. Each color phase can correspond to a different color, which generates at least a portion of a complex color image. In one embodiment, the step of activating at least one micro-mirror may include (c) activating, in a middle portion of a first of the two consecutive color phases, at least one micro-mirror to generate at least one a portion of an image in a first color. Notably, the middle portion may be in at least one of the middle or the end of the first color phase. In another embodiment, the activation step may include (d) activating, at about the beginning portion of a next color phase for a second color, the at least one micro-mirror to generate a portion of an image in the second. color. Step (b) can be repeated for the different micro-mirrors. The method can also include generating a complex image when generating
constituent color images ordered as blue, green and red. A white image can be generated with the use of a clear filter that does not impart a specific hue to the lens. The white image can be generated between the blue and red images.
Brief Description of the Drawings Preferred embodiments of the present invention will be described in more detail below, with reference to the accompanying drawings. Figure 1 is a schematic diagram illustrating one embodiment of a projection system in accordance with the inventive arrangements described herein. Figure 2 is a schematic diagram illustrating a color wheel configured in accordance with another embodiment of the present invention. Figure 3 is a signal flow diagram illustrating a conventional method for generating a complex color within a projection system. Figure 4 is a signal flow diagram illustrating a method for generating a complex color in accordance with one embodiment of the present invention. FIGS. 5A-5E are signal flow digests illustrating methods for generating various complex colors in accordance with other embodiments of the present invention.
Detailed description of the invention The present invention relates to a projection system and to a method related thereto. In accordance with the innovative arrangements, a projection system is described wherein the visible artifacts, for example, the rainbow artifacts can be reduced Within the current projection systems, the images of multiple colors are generated by displaying the images with color components in a rapid succession. That is, a green image is shown, then a red image after a blue image When one is shown after the other in rapid succession, the human eye perceives a single image of multiple colors When the amount of time between the integrating images increases, observers can perceive the rainbow artifacts. observer em piece to discern visually the color images, the individual and the integrating, that form the images with Multiple colors This can be exacerbated when the observer momentarily loses focus, for example, by the vibrations caused simply by eating or moving his head. In accordance with the inventive arrangements described here, visual artifacts, including artifacts of arc i ris they can reduce when displaying imaging images of a multi-color image in a particular order that depends on the l uminosity of each color Also, the time between the integrating color images or the portions of them, forms a multiple image colors that can be reduced and / or minimized
Figure 1 is a schematic diagram illustrating an embodiment of a projection system 100 in accordance with the inventive arrangements described herein. As shown, the system 100 may include a light source 105, a color wheel 110, a micro device 115 digital mirror (DMD), and a projection lens 120 The light source 105 can provide a white light source that can be directed towards the color wheel 110 One or more control processors (not shown) can also be included to generate and providing the control signals to the DMD 115 and coordinating the rotation of the color wheel 110 with the operation of the DMD 115. In accordance with one embodiment, the color wheel 110 may include three different color filters. The color wheel 110 may include a filter 125. of blue light, a green light filter 130, and a red light filter 135 The color wheel 110 rotates so that each of the color filters 125-135 is exposed to the source 105 of light for a predetermined period of time, referred to as color phase The color wheel 110, for example, can rotate in a clockwise direction, indicated by the arrow 155 According to this, the sequence of light with color that passes to the DMD 115 is blue, green and red, which is repeated as the chromatic wheel 110 continues to rotate. However, it must be appreciated that the wheel chromatic 110 can rotate in a counter-clockwise direction In that case, color filters 125-135 can be arranged so that the color sequence is again blue, green, red Other color sequences can be used With reference to the modality where blue, green and red form the sequence, however
a higher quality image can be achieved Green color has greater luminosity than blue and red When placing higher brightness colors, such as green, between lower luminosity colors, such as red and blue, can be reduced visual artifacts, which leads to a higher quality image Although the present invention will be described in great part with reference to a color wheel, it should be appreciated that other mechanisms can be used to generate different colors of light. this, the present invention is not only imitated by the use of a chromatic wheel. Rather, any mechanism with the ability to generate light with color in a sequential order, as described herein, can be used in addition, although the illustrative mode shows a chromatic wheel 1 1 0 which is in the optical path between the source 105 of l uz and the DMD 1 1 5, the color wheel can be in the optical path and between the DMD and the projection lens 1 50 The DMD 1 1 5, as it is known, may include a micro-mirror array 140 The micro-mirror arrangement may include approximately 1.3 million mirro-mirrors, each mounted on an articulated mechanism Each micro-mirror can be tilted, with the use of the articulated mechanism, towards the light source 1 05 or away from the light source 1 05. When it approaches the light source 1 05, it is said that the micro-mirror may be in an "on" or "activated" state When tilted away from the source 1 05 of lz, a micro-mirror may be said to be in the "off" or "off" state 1 20 projection lens can receive reflected light from the a fix
140 of micro-mirror Light, which forms a series of color images, results in a multi-color image 145 perceived to be projected onto a projection surface 1 50. During operation, the color wheel 1 1 0 can rotate at a fixed rotational speed, so that each color light filter 125-1 is passed through a 1 x 60 beam from the 1 0 uz source for a predetermined period of time, called the color The lzz 1 65 with color arising from the chromatic wheel 1 10 advances to the array 140 of micro-mirrors of the DMD 1 1 5 The control signals are provided to the DM D 1 1 5 to control the individual micro-mirrors of the array Micro-mirror 140 The micro-mirrors can be activated and deactivated during consecutive color phases, wherein each color phase corresponds to a particular color. That is, during a blue phase, while the blue light impinges on the array. of the micro-mirror, one or more of the micr o-selected mirrors can be activated This results in a blue image 1 70 to be sent to the lens 1 20. During the green phase, when the green light hits the micro-mirror array 140, another grouping of one or more selected micro-mirrors can be activated, which pces an image 1 75 green This same can be done during the color phase where the red light hits the micro-mirror array 140, which pces a red image 1 80 At each color phase, each individual micro-mirror can be activated for an amount of time corresponding to the intensity of color to be reflected within that color phase. As mentioned, each
micro-mirror can correspond to a single pixel within the images 170, 1 75 and / or 180 of color, as well as the resulting image 145 Thus, the i 1 blue 1 70 may have pixels of different shades of blue, corresponding to the individual micro-mirrors activated by varying times The green image 1 75 may have different shades of green, and the red image 180 may have different shades of red The rapid successive display of the images 1 70-1 80 of color gives as result a multi-color image 145 displayed on the deployment screen 150 Conventional deployment systems operate to activate the individual micro-mirrors of the micro-mirror display at the start of each successive color phase. This is, the control signals are synchronized with the rotation of the chromatic wheel 1 10, so that the DMD 1 1 5 starts to activate the individual micro-mirrors at the start of each color phase. For example, to generate a color siena formed of blue and green, it will be necessary to generate a blue image followed by a green image. Thus, at the beginning of the blue phase, conventional projection systems will activate the micro-mirrors necessary to generate the blue image at the beginning of the blue phase. blue phase The individual micro mirrors can be deactivated during the blue color phase according to the intensity of the respective pixel to which each micro-mirror corresponds At the beginning of the green phase, the selected micro-mirrors needed To generate the green screen, the individual micro mirrors can be deactivated during the green phase,
according to the intensity of the pixel to which each pixel corresponds. The resulting image is an image that has a shadow that depends on the intensity of each respective blue and green image, or portions thereof. The resulting image can be referred to as a complex image, since the image includes colors generated with the use of two or more color filters of the chromatic wheel 1 1 0. Notably, the aforementioned example can also be applied at a pixel level, where the same micro-mirror is activated at the start of successive blue and green phases. In any case, it should be appreciated that the cycle described herein can be repeated as necessary to produce a series of complex images to reproduce the movement. Figure 2 is a schematic diagram illustrating a color wheel 200 configured in accordance with another embodiment of the present invention. The color wheel 200 includes four light filters. In addition to the blue light filter 205, a green light filter 21 0, a red light filter 21 5, a clear filter 220 have been included. The clear filter 220 allows the white light of a light source to pass freely. In one embodiment, the clear filter 220 may be placed between the green light filter 210 and the red light filter 21, as shown. In another embodiment, however, the clear filter 220 may be placed between the blue light filter 205 and the green filter 21 0. The introduction of the clear filter 220 reduces the length of the color phases for the other colors. Because of this, the brightness available to project a fully saturated color is reduced a little. This manifests itself as a loss in brilliance available for colors
Fully saturated With regard to partially saturated colors, more common, however, the available brightness can increase as the clear filter 220 projects the white light that includes the blue, green and red light components, better than a single color component In any case, the blue light filter 205, the green light filter 21 0 and the red filter 21 5 can continue to be used to adjust the shadow of an image as required and to generate any target intensity that is necessary beyond what is provided during the portion of the clear filter 220 of the wheel. In Figure 2, the clear filter 220 may be to be approximately the same size as the other filters 205. However, in other embodiments, the clear filter 220 may be made smaller than the other filters 205-21 5 of colored light. That is, the portion of the circumference of the chromatic wheel 200 occupied. by the fi ltr or 220 light, represented by line 225, may be shorter in length than the other filters 205-21 5 of color light This produces a color phase for white light that is shorter in duration than the color phases for other colors generated by the chromatic wheel 200 Figure 3 is a signal flow diagram illustrating a conventional method for generating a complex color The signal flow diagram illustrates the states of the control signal with respect to the phase sequence repetitive color In this way, the signal flow graph illustrates the activation and deactivation states corresponding to a determined micro-mirror within a micro-mirror array during the consecutive color phases. The color generated in Figure 3 is a
medium yellow fully saturated composed of red and green As shown the color phase is red, green and then blue In traditional way, the micro-mirror can be activated at the beginning of the red and green phases and stay on for a certain portion or all of each color phase As a result, the time between the generation of the red and green images, in this case, unique pixels is maximized as the micro-mirror is activated at the beginning of the red and green phases. the time "t" is long Figure 4 is a signal flow diagram illustrating a method for generating a complex color in accordance with an embodiment of the present invention As shown, the color phase sequence has been changed to blue, green and then red. Furthermore, the control signal no longer activates micro-mirrors only in the start portions of each color phase. Rather, the control signal can activate a micro-mirror at the beginning or at the midpoint within a color phase as shown A midpoint may correspond to any portion of the color phase excluding the start For example, a midpoint may correspond to a portion in a phase of color that is in the middle or before the final portion of the color phase To generate a fully saturated medium yellow composed of green and red, the control signal causes the micro-mirror to be activated during both phases of respective color. , in a remarkable way, the micro-mirror is activated towards the middle or at the end of the green phase, that is to say in an average portion. The micro-mirror is activated or can remain activated, at the beginning of the red phase
In this way, the time between the successive activations of the micro-mirror for the green and red phases is reduced and / or minimized. This reduces the time between the green and red pixels that make the yellow color fully saturated. implements on a larger scale for multiple micro-mirrors, the time between the successive color images, in this case the green and red images, is reduced and / or minimized by reducing the time between these pixels and / or images, the number and magnitude of the rainbow artifacts perceived by the system can be reduced. Figures 5A-5E are signal flow diagrams illustrating methods for generating various complex colors in accordance with other modalities of the present invention. As shown, the white color has been included in the color phase sequence to adapt the case where the clear filter is introduced into the chromatic wheel As described herein, and is indicated in Figures 5A-5E the duration of the white phase is shorter in time than the other color phases. In any case, as was the case with Figure 4, the colors shown are not intended to be exhaustive of the possible list of complex colors that are may generate with the use of the methods described herein. Rather, the selected complex colognes have been presented as examples for the purpose of broadening the scope of the present invention. FIG. 5A illustrates a method for producing a dark gray color in accordance with the invention. with one embodiment of the present invention The control signal causes the micro-mirror to be activated during the white phase. Notably, the control signal is changed to the state
turned on during the col white phase That is, the control signal does not need to enter the on state at the beginning of the white phase. FIG. 5B illustrates a method for producing a dark yellow color in accordance with the inventive arrangements here. exposed The dark yellow color can be produced in green, white and light red The control signal is placed in the on state, approximately in the middle during the green phase, that is, in the middle portion The signal returns to the on state during the white phase in the middle portion The control signal is placed again in the on state near or at the start of the red phase In this way, that is, by moving the pulse for the green phase later in time, keeping the white pulse close to the middle part of the col or white phase, and moving the impulse for the red phase towards the start, the time "t" between the respective lit states will be educe and / or minimize Figure 5C illustrates a method for producing a total white color in accordance with the inventive arrangements described herein. The total white color may be produced by keeping the active micro-mirror during each respective color phase, as shown. that the clear section of the color wheel was used to generate all color components simultaneously, this total white color can be brighter than the normal color wheel white without a clear segment Figure 5D illustrates a method for producing a total yellow color according to the inventive arrangements described herein. The total yellow color may be formed of green, white and red light.
shows, the control signal has been placed in the on state during all of each of the green, white and red phases. The control signal has been placed in an off state during the blue phases. Figure 5E illustrates a method for producing a light yellow color according to the inventive arrangements described herein. The light yellow color can be formed of green, white and red light. The control signal is placed in the ignition state approximately half way through the color phase. green, in a middle portion The control signal stays on until approximately half through the white phase, point at which it is placed in an off state The control signal is then returned to the on state at or approximately at the beginning of the red color phase By shifting the impulse to the green phase back in time and maintaining the impulses for the white and red phases or near the start of each respective color phase, the amount of time between the consecutive micro-mirror activations for different color phases is reduced and / or minimized. As noted, this can reduce the perceptible rainbow artifacts within the projection systems In order to maximize the effectiveness of the clear segment of the color wheel, the following technique can be used First, for a given pixel color, the desired magnitudes of red are calculated, green and blue After, the light segment is used for a period of time that is equivalent to the shortest activation time of the three color phases When the activation time shortest red, green or blue is more
As long as the color phase of the clear segment is used, then the total time of the color phase of the light segment is used. The activation time for each red, green and blue is reduced by the amount of time that the light color segment is active. However, it should be appreciated that other methods can be used to use the clear segment of the color wheel and that the present invention is not limited to the technique described above. Although the foregoing is directed to the preferred embodiment of the present invention, other embodiments of the invention may be contemplated without departing from the basic scope thereof, and the scope is determined by the following claims.